Fluorinated surfactants

ABSTRACT

A composition of formula I
 
[Rf(CH 2 ) m (O) n ] x -A
 
wherein
         R f  is a straight or branched perfluoroalkyl group having from about 2 to about 20 carbon atoms, or a mixture thereof,   m is a positive integer equal to or greater than 3,   n is 0 or 1,   x is 1 to about 3, and   A is  − SO 2 B,   B is N(R 2 ) 2  or N(CH 2 CH 3 )(CH 2 CH 2 OH),   R 2  is C 1  to C 4  alkyl.

BACKGROUND OF THE INVENTION

Perfluoroalkylethyl iodides, C_(k)F_((2k+1))CH₂CH₂I, termed “Telomer B iodides”, are prepared by insertion of an ethylene molecule into the perfluoroalkyl iodides of the structure C_(k)F_((2k+1))I, “termed Telomer A iodides”. Perfluoroalkylethyl iodides are starting materials for the preparation of fluorinated surfactants and treatment chemicals to provide surfaces with hydrophobic and oleophobic properties. Compounds made from such iodides include, for example, perfluoroalkylethyl(meth)acrylates and various other compounds containing the perfluoroalkylethyl group, and find commercial use in the modification of surface properties. See, for example U.S. Pat. No. 3,721,706.

For surfactants and surface treatment agents with fluorochemical chains longer perfluoroalkyl chains contain a higher percentage of fluorine at a given concentration and provide better performance. However, fluorinated materials are more expensive. Reduction of the fluorine content with delivery of the same or higher performance is therefore desirable. Reducing the fluorine content would reduce the cost, but it is necessary to maintain product performance.

It is desirable to improve surfactant or surface treating agent performance and to increase the fluorine efficiency, i.e., boost the efficiency or performance of the surfactants or treating agents so a lower proportion of the expensive fluorine component is required to achieve the same level of performance, or to have better performance using the same level of fluorine. It is also desirable to have an economical pathway for preparation of such fluorine efficient surfactants and surface treating agents from perfluoroalkyliodides.

Two methods for the preparation of perfluoroalkylethyl(meth)acrylates from perfluoroalkyliodides are:

-   (1) reaction of the perfluoroalkylethyl iodide with a (meth)acrylic     acid salt such as potassium (meth)acrylate, as described by Fasick     et al. in U.S. Pat. No. 3,239,447; and -   (2) reaction of the perfluoroalkylethyl iodide with oleum and     further hydrolysis of the sulfates with water in sulfuric acid to     yield perfluoroalkylethanol, as described by Day in U.S. Pat. No.     3,283,012, followed by esterification with (meth)acrylic acid or     transesterification with an alkyl (meth)acrylate.     The first process is accomplished in a single step but yields are     lowered by the formation of byproduct perfluoroalkylethylene. The     second process involves two reaction steps, the use of oleum and     sulfur trioxide, but is free of byproduct perfluoroalkylethylene.

There is a need for surfactants and surface treating agents providing equivalent or improved performance while reducing the proportion of fluorine required due to its expense, and for economical pathways to such products. The present invention provides such surfactants having higher fluorine efficiency and an improved method of making certain surfactants.

SUMMARY OF THE INVENTION

The present invention comprises a composition of Formula I [R_(f)(CH₂)_(m)(O)_(n)]_(x)-A wherein

R_(f) is a straight or branched perfluoroalkyl group having from about 2 to about 20 carbon atoms, or a mixture thereof,

m is a positive integer equal to or greater than 3,

n is 0 or 1,

x is 1 to about 3, and

A is —P(O)(OR¹)_(y)(OM⁺)_(3-y-x), —C(O)CH(SO₃ ⁻M⁺)CH₂C(O)⁻, ⁻(CH₂CH₂O)_(d)(CH₂CHR²O)_(e)R³, or ⁻SO₂B,

M⁺ is an alkali metal ion, NH₄ ⁺, or NH₂(CH₂CH₂OH)₂,

B is N(R²)₂ or N(CH₂CH₃)(CH₂CH₂OH),

R¹ is C₁ to C₃ alkyl, and

R² is C₁ to C₄ alkyl,

R³ is H or CH₃,

y is 0 to about 1,

d is 0 to about 16,

e is 0 to about 16, provided that (d+e) is from about 3 to about 16.

The present invention further comprises a method of lowering the tension at the surface of contact between two phases comprising contacting said surface with a composition of Formula I [R_(f)(CH₂)_(m)(O)_(n)]_(x)-A wherein

R_(f) is a straight or branched perfluoroalkyl group having from about 2 to about 20 carbon atoms, or a mixture thereof,

-   -   m is a positive integer equal to or greater than 3,     -   n is 0 or 1,     -   x is 1 to about 3, and

A is —P(O)(OR¹)_(y)(OM⁺)_(3-y-x), —C(O)CH(SO₃ ⁻M⁺)CH₂C(O)⁻, ⁻(CH₂CH₂O)_(d)(CH₂CHR²O)_(e)R³, or ⁻SO₂B,

M⁺ is an alkali metal ion, NH₄ ⁺, or NH₂(CH₂CH₂OH)₂,

B is N(R²)₂ or N(CH₂CH₃)(CH₂CH₂OH),

R¹ is C₁ to C₃ alkyl, and

R² is C₁ to C₄ alkyl,

R³ is H or CH₃,

y is 0 to about 1,

d is 0 to about 16,

e is 0 to about 16, provided that (d+e) is from about 3 to about 16.

DETAILED DESCRIPTION

Herein tradenames are shown in upper case.

The term “(meth)acrylates” as used herein includes both acrylates and methacrylates.

The present invention comprises surface active compositions or surfactants of formula [R_(f)(CH₂)_(m)(O)_(n)]_(x)-A, Formula I, wherein R_(f) is a straight or branched chain perfluoroalkyl group having 2 to about 20 carbon atoms, or a mixture thereof;

m is a positive integer greater than or equal to 3;

n is 0 or 1;

x is 1 to about 3 and is determined by the valence of A; and

A is —P(O)(OR¹)_(y)(OM⁺)_(3-y-x), —C(O)CH(SO₃ ⁻M⁺)CH₂C(O)⁻, ⁻(CH₂CH₂O)_(d)(CH₂CHR²O)_(e)R³, or ⁻SO₂B,

wherein

M⁺ is an alkali metal ion, NH₄ ⁺, or NH₂(CH₂CH₂OH)₂,

R¹ is C₁ to C₃ alkyl, and

R² is C₁ to C₄ alkyl,

R³ is H or CH₃,

B is N(R²)₂ or N(CH₂CH₃)(CH₂CH₂OH),

y is 0 to about 1,

d is 0 to about 16,

e is 0 to about 16, provided that (d+e) is from about 3 to about 16.

The iodides of the structure R_(f)(CH₂)_(m)I wherein R_(f) and m are defined as above precursors and used in the preparation of the compositions of the present invention. These iodides are prepared by reacting R_(f)I with ethylene under pressure at elevated temperatures and optionally in the presence of a free radical source as described by Brace in U.S. Pat. No. 3,145,222. The alcohols of the structure R_(f)(CH₂)_(m)OH wherein R_(f) and m are as defined above can be prepared by contacting the iodide R_(f)(CH₂)_(m)I with N,N-dimethylformamide and water at an elevated temperature (about 120° C.).

Phosphate surfactants of the present invention are of Formula I wherein A is P(O)(OR¹)_(y)(O⁻M⁺)_((3-y-x)), and

x is 1 to about 2.

R¹ is preferably iso-propyl. The phosphate surfactants of the present invention also can contain phosphate byproducts such as mixed pyrophosphates of formula [R_(f)—(CH₂)_(m)O]_(x)P(O)(OR¹)_(y)—O—P(O)[R_(f) (CH₂)_(m)O]_(x)(OR¹)_(y), and non-fluorinated phosphates, such as R¹O—(NH₄O)₂P(O) due to the reaction of the R¹OH alcohol. Such byproducts have no significant effect on the surfactant properties of the compositions of the present invention. The phosphate surfactants of the present invention are prepared by reacting the alcohol R_(f)(CH₂)_(m)OH sequentially with phosphorus pentoxide. This is followed by adding R¹OH preferably isopropanol to ensure a complete reaction. It is then neutralized with aqueous ammonia or other water-soluble amines such as NH(CH₂CH₂OH)₂. These phosphate surfactants even with a short perfluoroalkyl chain (such as when R_(f) is perfluorobutyl and m=3 or 4), when dissolved in water provide a greater decrease in surface tension than the corresponding surfactants with m=2 on an equal weight, fluorine percent, or equimolar concentration basis. Additionally they result in a more efficient use of the fluorine moiety, that is a greater surface tension decrease is obtained with less fluorine, providing an economic advantage.

The polyalkylene oxide surfactants of the present invention are of Formula I wherein A is (CH₂CH₂O)_(d)(OCH₂CH₂OR²)_(e)OR³. The polyalkylene oxide surfactants are prepared by contacting R_(f)(CH₂)_(m)OH with sodium borohydride and ethylene oxide.

The sulfosuccinate surfactants of the present invention are of Formula I wherein A is the divalent group ⁻C(O)CH(SO₃ ⁻M⁺)CH₂C(O)⁻ and x is 2. These surfactants are prepared by reacting R_(f)(CH₂)_(m)OH with maleic anhydride and treating the maleate diester with sodium bisulfite.

The surfactants of Formula I wherein A is SO₂B are prepared by reaction with a sulfonyl halides of the structure R_(f)(CH₂)_(m)S(O₂)X, and wherein X is a halogen. These are prepared by reacting R_(f)(CH₂)_(m)I wherein R_(f) and m are defined as above in Formula I with potassium thiocyanate, followed by oxidation with chlorine in the presence of water (e.g., as in U.S. Pat. No. 3,825,577). When B is N(R²)₂, the sulfonyl halide is reacted with H₂N(R²)_(f)N(R²)₂ wherein each R² is independently C₁ to C₄ alkyl, and f is 2 or 3, typically in an ether solvent. When B is ⁻N(CH₂CH₃)(CH₂CH₂OH), the sulfonyl halide is reacted first with H₂NC₂H₅ and then with ethylene oxide.

These anionic and non-ionic compositions are useful as a general surfactant at loadings much lower than the corresponding compositions wherein m is 2. They are also useful as leveling agents for various surfaces.

The compositions of claim 1 can further comprise a surface treatment agent. Suitable surface treatment agents include those which provide a method of lowering the tension at the surface of contact between two phases comprising contacting said surface with a composition of Formula I [R_(f)(CH₂)_(m)(O)_(n)]_(x)-A wherein

R_(f) is a straight or branched perfluoroalkyl group having from about 2 to about 20 carbon atoms, or a mixture thereof,

m is a positive integer equal to or greater than 3,

n is 0 or 1,

x is 1 to about 3, and

A is —P(O)(OR¹)_(y)(OM⁺)_(3-y-x), —C(O)CH(SO₃ ⁻M⁺)CH₂C(O)⁻, ⁻(CH₂CH₂O)_(d)(CH₂CHR²O)_(e)R³, or ⁻SO₂B,

M⁺ is an alkali metal ion, NH₄ ⁺, or NH₂(CH₂CH₂OH)₂,

B is N(R²)₂ or N(CH₂CH₃)(CH₂CH₂OH),

R¹ is C₁ to C₃ alkyl, and

R² is C₁ to C₄ alkyl,

R³ is H or CH₃,

y is 0 to about 1,

d is 0 to about 16,

e is 0 to about 16, provided that (d+e) is from about 3 to about 16.

In another embodiment, the present invention is directed to a process for the preparation of perfluoroalkylalkyl (meth)acrylates by reaction of a (meth)acrylate salt with a perfluoroalkylalkyl iodide of the structure R_(f)(CH₂)_(m)I, wherein R_(f) and m are as defined above in Formula I. Unexpectedly, the reaction yield when m is greater than or equal to 3 is about 95% and is not diminished by the formation of byproduct ethylenic compounds as occurs in the prior art reaction wherein m is 2. The corresponding molar yield when m is 2 is about 80-85%. The (meth)acrylate salt used in this process is an alkali metal salt and is preferably potassium or sodium (meth)acrylate. The reaction to produce the perfluoroalkylalkyl (meth)acrylate is: R_(f)(CH₂)_(m)I+MOC(O)CR³═CH₂→R_(f)(CH₂)_(m)OC(O)CR³═CH₂+MI wherein

R³, R_(f) and m are as defined above in Formula I. The improved process of the present invention is useful to prepare perfluoroalkylalkyl acrylates and perfluoroalkylalkyl (meth)acrylates wherein m is greater than or equal to 3. The perfluoroalkylalkyl (meth)acrylates prepared by the process of the present invention are useful as monomers in emulsion or solution co-polymerization with (meth)acrylates, vinyl chloride, vinylidene chloride and other olefins to prepare useful co-polymers. These polymers and copolymers wherein m is greater than or equal to 3 provide soil resistance, stain resistance, oil repellency and water repellency to substrates, such as textiles, stone, tiles, paper, etc.

The surfactant compositions of the present invention, and the perfluoroalkylalkyl (meth)acrylates prepared by the process of the present invention have increased fluorine efficiency compared to analogous prior art compositions wherein m is 2. By increasing m, the hydrocarbon portion of the composition is increased relative to the fluorine portion, yet the surface effect performance is the same or better.

Materials and Test Methods

VAZO-67 is 2.2′-azobis(2-methylbutyronitrile) and is available from E. I. du Pont de Nemours and Company, Wilmington Del.

Perfluoroalkyl iodides used as reactants in the Examples were prepared as follows:

Perfluorohexyl iodide (67 g, 150 mmol) and VAZO-67 (0.45 g, 1.6 mol. %) were charged to a 450 mL shaker tube and purged with nitrogen. The tube was charged with ethylene and heated to 80° C. for 4 hours with 1200 psig of ethylene. By GC/FID analysis, the product of the reaction contained C₆F₁₃CH₂CH₂I (2.4%), C₆F₁₃(CH₂)₄I (76.9%), C₆F₁₃(CH₂)₆I (14.7%), C₆F₁₃(CH₂)₈I (5.3%). Other homologs of the perfluoroalkyl iodides were prepared using the same process using the analogous starting iodides.

Perfluoroalkyl alcohols used as reactants in the Examples were prepared as follows:

C₆F₁₃—(CH₂)_(m)—I (6.0 g, m=2 [6.8%], 4, 6, 8 with average MW=403) was charged into the round bottom flask and reacted with N,N-dimethylformamide (20 eq.) and water (8 eq.) at 120° C. for 15 h to obtain complete conversion into the C₆F₁₃—(CH₂)_(m)—OH (with <1% of olefin elimination products by GC/FID). The reaction mixture is further washed three times with water, and product dried in vacuum to remove the residual water and N,N-dimethylformamide. Other homologs of the perfluoroalkyl alcohols were prepared using the same process using the analogous starting materials.

Test Method 1. Measurement of Surface Tension.

The surface tension measurements of anionic surfactants were measured in deionized water by the use of Wilhelmy plate (Kraus USA, Nazareth, Pa.) method on an automated Kiruss tensiometer used in accordance with the manufacturers' manuals. Lower surface tension values at a given concentration denote improved surfactant properties.

EXAMPLES Example 1

To a round-bottom flask fitted with a mechanical stirrer and sparged with nitrogen was added C₄F₉(CH₂)₄OH (40.1 g). While stirring at 23-24° C., phosphorus pentoxide (8.8 g) was added in portions over a period of 5.5 h. The reaction mixture was then heated to 95° C. for 17 h. After heating, isopropanol (37.8 g) was added over a period of 2 h while the mixture cooled from 95° C. to 65° C. Aqueous ammonia solution (15.9 g, 27%) was then added to the reaction mixture; the temperature rose from 65 to 68° C. during the addition. Deionized water was added next, and the mixture was stirred at 60° C. for 2 h and cooled to room temperature yielding an aqueous solution of the anionic surfactant. The surface tension of the surfactant was measured in deionized water using Test Method 1. Results are listed in Table 2.

Examples 2 and 3

The procedure of Example 1 was repeated replacing the C₄F₉(CH₂)₄OH with an equimolar amount of the perfluoroalkylalkanols C₄F₉(CH₂)₃OH (Example 2), or C₆F₁₃(CH₂)₄OH (Example 3) alcohols to produce the corresponding phosphate surfactants. The surface tension was measured in deionized water using Test Method 1. Results are in Table 2.

Comparative Example A

The procedure of Example 1 was repeated replacing the C₄F₉(CH₂)₄OH with an equimolar amount of the perfluoroalkylethanol C₄F₉CH₂CH₂OH to produce the corresponding phosphate surfactant as a control example.

³¹P NMR was used to determine the mole % of the various phosphates in the above Examples as shown in Table 1.

TABLE 1 Phosphate formula, Example 1 Example 2 Example 3 where R_(f)= C_(k)F_((2k+1))− k = 4, m = 4 k = 4, m = 3 k = 6, m = 4 R_(f)—(CH₂)_(m)O—(NH₄O)₂P(O) 38.3 34.6 23.4 (R_(f)—(CH₂)_(m)O)₂—(NH₄O) P(O) 31.2 40.6 36.4 (CH₃)₂CHO—(NH₄O)₂P(O) 11.8 2.2 6.0 (R_(f)—(CH₂)_(m)O) (CH₃)₂CHO—(NH₄O)P(O) 8.0 — 2.5 (R_(f)—(CH₂)_(m)O)₃P(O) 4.6 — — Pyrophosphates* (total) 6.0 22.4 31.6 *Pyrophosphate byproducts.

TABLE 2 Surface tension* k = 4, m = 2 Conc. Comp. Ex. A k = 4, m = 3 k = 4, m = 4 k = 6, m = 4 (wt %) (Control) Ex. 1 Ex. 2 Ex. 3 0.0001 — 67.22 52.31 67.94 0.0005 76.46 44.29 49.00 38.89 0.001 46.61 37.12 46.82 36.51 0.005 42.52 29.46 38.05 20.49 0.01 38.76 27.06 33.13 19.77 0.05 32.91 18.95 24.13 17.10 0.1 25.94 16.62 19.48 16.76 0.2 19.26 16.61 15.37 16.73 0.5 16.47 16.38 15.34 15.30 1 — 16.25 15.49 14.56 *dyne/cm, (×10⁻³ = N/m)

Table 2 shows that, at weight % concentrations of 0.0001% to 0.5%, the surface tension was lower (greater surfactant effect) for the surfactants of the present invention (m greater than 2) than for the corresponding surfactant having n=4, m=2.

Example 4

Perfluoroalkylalkyl alcohol and sodium borohydride (5 mol. %) is charged into a round bottom flask equipped with mechanical stirring and a cold finger condenser (at about −70° C.) and reacted at 85-130° C. under nitrogen. The temperature is adjusted to 65-100° C., when ethylene oxide is fed over time to the reaction flask, maintaining conditions to avoid the formation of potentially explosive air-ethylene oxide mixtures and uncontrolled reaction of ethylene oxide with solid sodium borohydride). The reaction with ethylene oxide is continued at 65-100° C. until the required equivalents of ethylene oxide (typically about 5-10 equivalents) are consumed. Vacuum is applied to remove the residual ethylene oxide, and flask is refilled with nitrogen. The product perfluoroalkylalkyl polyethyleneglycol C_(k)F_((2k+1))—(CH₂)_(m)—O(CH₂CH₂O)_(d)—H is diluted with water and optionally other co-solvent for further use and surface tension measurements.

Example 5

Anhydrous potassium carbonate (0.66 g) was placed into 20 mL vial containing 10 mL of dimethylformamide and stirred at 70° C. for 1 h. Then C₄F₉—(CH₂)_(m)—I (0.84 g, m=2 (5%), 4, 6, 8, average MW=416) was added and the solution was stirred for additional 40 min at 70° C. Polyethylene glycol monomethyl ether (1.0 g, average MW=350) was added and the reaction mixture stirred at 70° C. for 20 h. GC/FID analysis showed >98% conversion of C₄F₉—(CH₂)_(m)—I. The reaction mixture was cooled to room temperature and 30 mL of deionized water was added. The product C₄F₉—(CH₂)_(m)O(CH₂CH₂O)_(d)—CH₃ was extracted from this solution using diethyl ether. The organic layer was washed with deionized water and dried with MgSO4. Solvent was removed under reduced pressure and the crude product was dried in a vacuum oven at 1 mmHg (133 1 kPa) at 90° C.

Example 6

1H,1H,2H,2H,3H,3H,4H,4H-nonafluorooctanol (C4F9CH2CH2CH2CH2OH, is prepared as described in Example 1, (58 g, 0.2 mol), maleic anhydride (9.8 g, 0.1 mol), p-toluene sulfonic acid monohydrate (2 g, 10 mmol) and 150 mL of toluene are stirred at reflux under dry nitrogen. Condensate from the continuous azeotropic distillation is collected in a Dean-Stark apparatus, returning the dry toluene to the reaction vessel. The water collected as a separate lower layer in the trap is greater than 90% of expected. The reaction mixture is cooled, washed with water, and the resultant organic (toluene) layer concentrated by rotary evaporation, leaving 66 g of an oily material. The reaction product is taken up in 500 g of diethylene glycol diethyl ether, and heated to 50° C. An aqueous solution of sodium bisulfite (NaHSO3, 14.5 g, 0.14 mol, dissolved in 80 mL of deionized water) is added. The mixture is heated to near reflux (95° C.) with evolution of gas. After 30 h at elevated temperature, solid material (65 g, 87% crude yield) is collected by filtration. The product is the sulfosuccinate ester. C4F9CH2CH2CH2CH2OOCCH2CH(SO3Na)COOCH2CH2CH2CH2C4F9.

Example 7

C_(k)F_(2kn+1)—(CH₂)_(m)—I (100 g) where a=6-16 and m=2 (7.3%), m=4 (72.54%), m=6 (18.4%) was treated with potassium acrylate (29.2 g), t-butanol (70 g), and hydroquinone (0.45 g) at 180° C. for 5 hours. The resulting product was filtered from insoluble salts and heated in vacuum to remove t-BuOH to obtain 88.8 g of C_(k)F_(2k+1)—(CH₂)_(m)—OC(O)CH═CH₂ acrylate. According to gas chromatography (GC) analysis the monomer obtained contained only 0.55% of C_(k)F_((2k+1)—)CH═CH₂. The acrylate was further washed with 200 mL of 10% NaHCO₃ aqueous solution preheated to 55° C., 200 mL of water (pH=7). The organic layer was phase separated and dissolved in 400 mL of THF. The solution was dried over MgSO₄, filtered, and the solvent was removed by heating in reduced pressure. 

What is claimed is:
 1. A composition of formula I [R_(f)(CH₂)_(m)(O)_(n)]_(x)-A wherein R_(f) is a straight or branched perfluoroalkyl group having from about 2 to about 20 carbon atoms, or a mixture thereof, m is a positive integer equal to or greater than 3, n is 1, x is 1, A is —SO₂B″ wherein, B is N(R²)₂ or N(CH₂CH₃)(CH₂CH₂OH), and R² is C₁ to O₄ alkyl.
 2. The composition of claim 1 further comprising a surface treatment agent.
 3. The composition of claim 2 wherein the surface treatment agent provides a surface effect with or without ironing which is shrinkage control, wrinkle free, permanent press, moisture control, softness, strength, anti-slip, antistatic, anti-snag, anti-pill, stain repellency, stain release, soil repellency, soil release, water repellency, oil repellency, odor control, antimicrobial, or sun protection.
 4. A method of lowering the tension at the surface of contact between two phases comprising contacting said surface with a composition of Formula I [R_(f)(CH₂)_(m)(O)_(n)]_(x)-A wherein R_(f) is a straight or branched perfluoroalkyl group having from about 2 to about 20 carbon atoms, or a mixture thereof, m is a positive integer equal to or greater than 3, n is 1, x is 1 to about 3, and A is —SO₂B″ wherein, B is N(R²)₂ or N(CH₂CH₃)(CH₂CH₂OH), and R² is C₁ to O₄ alkyl.
 5. The method of claim 4 wherein the composition acts as a leveling agent.
 6. The method of claim 4 wherein the phases are each independently a fibrous surface or a hard surface.
 7. The method of claim 4 wherein the composition is applied as a coating to a surface.
 8. The composition of claim 1 wherein n is 1, A is —SO₂B″ wherein and B is N(R²)₂. 